This application claims the benefit of Korean Application No. 2002-1850, filed Jan. 12, 2002, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus and method of suppressing a low speed ripple current of a single-phase inverter, and more particularly to an apparatus and method of suppressing a low speed ripple current of a single-phase inverter, which controls an output voltage of the single-phase inverter at an interval during which the low speed ripple current is generated, thus, preventing negative effects caused by the low speed ripple current.
2. Description of the Related Art
Generally, inverters to convert direct current (DC) power into alternating current (AC) power are used to control a speed of a motor. The inverters are classified into two types: three-phase inverters supplied with DC power, which is obtained by rectifying three-phase AC power, and single-phase inverters supplied with DC power, which is obtained by rectifying a single-phase AC power.
Low speed ripple voltage included in full-wave rectified DC power is higher when using the single-phase AC power compared to using the three-phase AC power, such that an input signal is unstable for a single-phase inverter. Accordingly, a low speed ripple current is generated in a motor driving current outputted from the single-phase inverter, thereby decreasing control performance of a motor and shortening the inverter""s life due to overheating of the motor. Therefore, in a control system for driving the motor using the single-phase inverter, it is required to effectively prevent negative effects caused by the low speed ripple current.
In the related art, various methods for suppressing the low speed ripple current are proposed with respect to the three-phase inverter. However, such methods are limited in that the methods are usefully applied on condition that the input signal of the three-phase inverter is comparatively stable. Accordingly, the methods are inappropriate for the single-phase inverter.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an apparatus and method of suppressing low speed ripple current of a single-phase inverter, which controls an output voltage of the inverter appropriately, thus, preventing negative effects caused by a low speed ripple current.
In order to accomplish the above and other objects, the present invention provides an apparatus to suppress a low speed ripple current to a motor, including: a power supply unit supplying single-phase alternating current (AC) power; a rectifying and smoothing unit rectifying and smoothing the single-phase AC power and outputting a direct current (DC) voltage indicative thereof; an inverter receiving and converting the DC voltage to a motor driving current to drive the motor; and a controller comparing an envelope detected from a ripple current in the motor driving current and a DC component extracted from the ripple current and generating a compared result therefrom, and controlling an output voltage from the inverter according to the compared result.
The present invention further provides a method of suppressing a low speed ripple current generated when a motor is driven, including: outputting a motor driving current from a single-phase inverter to the motor; determining whether a present interval is an interval during which a low speed ripple current is generated from the motor driving current; detecting an envelope from the low speed ripple current; extracting a DC component from the low speed ripple current when the present interval is the interval during which the low speed ripple current is generated; comparing the detected envelope with the extracted DC component and generating a compared result therefrom; and controlling an output voltage of the inverter according to the compared result.
To achieve the above and other objects, the present invention provides a method to suppress a low speed ripple current to a motor, including: supplying single-phase alternating current (AC) power; rectifying and smoothing the single-phase AC power and outputting a direct current (DC) voltage indicative thereof; converting the DC voltage to a motor driving current to drive the motor; comparing an envelope detected from a ripple current in the motor driving current and a DC component extracted from the ripple current and generating a compared result therefrom; and controlling an output voltage from the inverter according to the compared result.
To achieve the above and other objects, the present invention provides an apparatus suppressing a low speed ripple current to a motor, including: an inverter providing a motor driving current to the motor; and a controller detecting an envelope of the low speed ripple current in the motor driving current, extracting a DC component from the ripple current, comparing the detected envelope with the extracted DC component to determine whether to increase or decrease an output voltage from the inverter, and outputting a control signal indicative thereof to the inverter to suppress the low speed ripple.
To achieve the above and other objects, the present invention provides a method of suppressing a low speed ripple current of a single-phase inverter driving a motor, including: supplying single-phase alternating current (AC) power; generating a direct current (DC) voltage from the single-phase AC power; generating a motor driving current from the DC voltage to drive the motor; determining whether a present interval of the motor driving current is an interval during which the low speed ripple current is generated; detecting an envelope of the low speed ripple current when the present interval is the interval in which the low speed ripple current is generated; extracting a DC component from an output current of the inverter; comparing the extracted DC component with the detected envelope to determine whether to increase or decrease an output voltage of the inverter; and outputting a signal to the inverter corresponding to whether to increase or decrease the output voltage to suppress the low speed ripple current.
These together with other objects and advantages, which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.